Art of cracking hydrocarbons



May 24, 1932. E. c. HERTHEL ABT OF CRACKING HYDROCARBONS Filed April 16.1927 2 Sheets-Sheet e w RM E mr m N6 O WH. H m( A May 24, 1932. E. c.HERTHEL ART OF CRACKING HYDHOGARBONS 2 Sheets-Sheet 2 Filed April 16.1927 ATToRNYs INVENTOR Fayene (/ferfel BY w@ L7-f 'Inn-Unull H51! l...

nGCrW UIDwWWIm ww ww EMT-...bmw

. to cracking and the lcharge is heated to the Patented May 24, 1932UNITED Ns'rnfllas inserat PATENT carrier EUGENE c. Hamann or crnIcAGo,ILLINOIS, AssIGNon iro snrcnm mme coat- PANY, on NEW vonk, N.` Y.,

A CORPORATION 0F MAINE am or cnAcxme mnocnnons llippinatnminea April 1s,

This invention relates to improvements in cracking heavier hydrocarbonoils, such as gas oil, fuel oil and heavy residuesnfor the production oflighter hydrocarhon oils, such as gasoline and pressure distillates,there-V from hy distillation under pressure.

In the cracking of heavier petroleum oils in pressure stills for theproduction of gasoline or pressure distillates, there are formed duringthe cracking operation certain constituents of an asphaltic orpitch-like character. With continuation of the cracking operation., theamount of such constituents increases an there is a tendency fordeposits of carbon or coke to form on the heated walls of the still,thus necessitating the shutting down of the still for cleaning purposesbetween successive runs. The shutting down of the pressure still, thewithdrawal of the chargertherefrom, the cleaning ofthe still, therecharging of the still and the preliminary heating of the stlll tobring the fresh charge up to cracng conditions, all require time, andthe total amount ottime so required in ordinary commercial operationsmeansa corresponding reduction in the proportion of the time when thestill'isoperating for 'carrying out the desired cracking operation.

According to the present invention, the de- P position of pitch orcarbon on the heang surfaces of the pressure still is prevented orgreatly reduced, so thatoverheating or dan'- gcr of failure of theheating walls isvcorrespondingly prevented or reduced, and the timeVott' useful operation in a single run prolonged with correspondinglyincreased continuity of operation, reduced loss of working time andincreased production per still per day. A 4

When a pressure still is-charged with gas oil or other charging stocktohe subjected cracking temperature. the. cracking takes place in agradual and progressive manner and the 'lighter constituents produced bythe cracking operation which go to make up the pressure distillate 'areremoved from th still progressively during the cracking operation. @therconstituents, such as heavier hydrocarbons 'formed by thecrackdstituents gradually and progressivel ma serial no. 184,274. f

ing operation, may/ remain and mix with the charge inH the still. Asmall amount of asphaltic or pitchvlike constituents is pro-l gressivelyformed. Such constituents apthey may remain,

amount of such asphaltic or pitch-like con- '4 mcreases until eventuallythe amount o such constituents increases beyond the saturation point. sthe charge becomes su rsaturated there is an increasedl dangerofpdeposit of pitch or carbon on the heating walls of i the still,withcorresponding danger of over'- heating andfailure of the heated walls ifT 4of fresh feed and the withdrawal of pitchladen/tar so thatconcentration of pitch-like y K constituents in the still charge as awhole may "he maintained below the saturation oint. The pressurey stilltar, when operating'in this manner, contains a substantial percentage'of lighter oil and 'it is customary -to subject the pressure tar tosomeA distillation rocess to recover the content oi lighter oil orreturn to and retreatment in the cracking operation. For example, thetar may he distiiled Vto dryness at atmospheric pressure in a cokestill, the major portion ot the pitch-like constituents contained in thepressure tar `remaining in the still as coke. The distillate from suchoperation may then he returned tothe pressure still, together with freshcharging-stock, tor turther-,cracking treatment. it is also customf Aary to redistill or tract/innate crude pressure distillates, andtheheavier ends or 'bottoms from such redistillation or fractionationytreatment are frequently returned to the pressure still for furthercracking treatment.

In charging` stock which contains sulphur,

certain of vthe sulphur vcompounds appear to undergo cracking to formsulphur-contain- In order to convert the crude pressure disingconstituents, probably of an asphalt-like character, which areparticularly objectionable. Analyses of the carbon'deposits on theheating walls of cracking stills indicate that certain of thesesulphur-containing constituents have a preferential affinity for theheated surfaces, or tend to separate out on such surfaces, and causedepositscontaining lboth iron and sulphur in proportions approximatingthose of iron sulfide. Separation of certain of the more objectionablesulphur-containing, compounds from the pressure still charge or pressuretar is eX- ceptionally diiiicult as they have boiling points closelyapproximating -those of the pressure still chargingv stock. Accordingly,

while the majority of the less objectionable` pitch-like constituents in,the pressure tar may be converted into coke or left behind as anundistilled residue on redistillation the more objectionable,sulphur-containing compounds tend to remain in the distillate. If thisdistillate is returned to the pressure still for further crackingtreatment'the complete cycle tends progressively to increase theconcentration of the more objectionable sulphur-containing compoundsinthe pressure still charge. Similarly a large part of thesulphur-containing compounds which are carried'over from the pressurestill with the crude pressure distillate become concentrated in theheavier portions of the pressure distillate on redistillation orfractionation.

According to the present invention, the fresh pressure still chargingstock is treated to relnove the more objectionable sulphurcontainingcompounds before introduction to the pressure still. The proportion ofsuch compounds present in the pressure still charge during the crackingoperation due to the sulphur contained in the fresh charging stock isthereby materially reduced. While theremoval of the greater part of thesulphur compounds from the fresh charging stock may be readilyaccomplished by ordinary refiningVv methods, a suiiciently vigoroustreatment to remove the most refractory sulphur compounds is notcommercially practicable from an' economic standpoint, and Where only apart of the sulphur compounds'are removedl by pretreatment of thecharging stock, those which remain become concentrated in the "pressurestill charge, as above described, on

reintroduction of distillates from the tar or of heavier portions of thepressure distillate to the pressure still. Further, according to thepresent invention, however, both such tar distillates and heavierportions of the pressure distillate, to the extent that they arereturned to the pressure still for further cracking treatment, aresubjected to a desulphurizing treatment before reintroduction to thepressure still.

compoundsy by treatment with a clay tillates-from the usual pressurecracking operations into marketable products, such as gasoline or motorfuel, it is generally necessary, in addition to redistillation orractionation, to further treat the distillate, for example with an acidand alkali, to remove the sulphur and unstable unsaturated compoundswhich decolnpose on prolonged standing and exposure to sunlight to formgummy and resinous bodies. In some cases, crude pressure, distillatesare treated to remove the sulphur and gum-forming constituents prior toAcrude pressure distillate is treated in this manner prior toredistillation, the pressure distillate bottoms may advantageously bereturned directly to the pressure still without further treatment. Thedesulphurizing treatment applied tothe fresh charging stock mayadvantageously be combined' with the similar treatment of tardistillatesto be recycled, as well as with any further treatment of theheavier portions of the pressuredistillate bottoms, as where the crudepressure distillate is not subjected to a desulphurizing operationbefore redistillation or fractination.

By treating the stocks to be recycled to the pressure still to removemore objectionable sulphur-containing compounds, in accordance with thepresent invention, the average concentration of such constituents in theaverage pressure still charge may be repressed wlthout requiringIunusual or expensive treatmentof the fresh charging stock.

The desulphurizing treatment may be carried out-byr any of the knownmethods, such as agitation with sulphuric acid and subsequentneutralization of the oil with an alkaline solution. One particularlyadvantageous method of carrying out the desulphurizing operation,however, is intimately to contact the oil with sulphuric acid in amechanical treater as hereinafter described, and after separating anyremaining acid and acid sludge, to remove any remaining acid or fullersearth, the clay 'or fullers earth with the constituents absorbed thereinbeing separatedv from the oil either directly or after' aol settling `bya filtering operationor other suitable treatment. y

The invention will be further described in connection with theaccompanying drawings, illustrating in a diagrammatic and somewhatconventional manner, one particularly advantageous embodiment of theimproved method of operation of the invention and arrangement ofapparatus adapted for the practice of the lnvention, but it is intendedand will be understood that the invention is illustrated thereby but isnot limited thereto. In the drawings:

Fig. 1 is a flow sheet diagrammatically illustrating the sequence ofsteps in a preferred method of operation'according to the presentinvention.

Fig. 2 shows an arrangement of apparatus, partly in section and partlyin elevation, adapted for the practice of the invention.

Referring to Fig. 2, the pressure still shown is of the general typedescribed and illustrated in U. S. Patent No. 1,285,200 issuedtoSinclair Retning "Company on an application of E. W. Isom filedNovember 19, 1918, and comprises a bulk supply tank 2, a battery ofheating tubes 3 arranged in asuitable furnace 4, and circulatingconnections 5, 6 and 7 whereby oil may be circulated by the pump 8 fromand to the bulk supply tank through the battery of heat-ing tubes inwhich it is heated to a cracking temperature. The vapors generated inthe cracking operation pass through the reflux tower 9, and refluxcondensate, together with unvaporized fresh oil when fresh oil isintroduced to the refluxing f operation, is returned to the crackingstill through connection 10. Fresh charging stock may be supplied to thereiux tower from the tank 11 by the pump 12 through lines 13 and 14. Aportion of the fresh charging stock may be introduced to the stillthrough the circulating pump bearings by branch connection 15 to cooland lubricate the same. Vapors escaping from the reflux tower 9 passthrough line 16 to condenser 17, from which condensate passes toreceiver 18 which may be of the usual type employed in connection withpressure cracking stills. The crude pressure distillate withdrawn fromreceiver 18 may be charged directly to the reiux tower 19 on the rerunstill 20` through connections 21 and 22 by means of the pump 23,

and fractionally distilled therein. The vapors generated in the rerunstill are passed to the condenser 24- from which the distillate of thedesired end point is discharged through connection 25, for example, tostorage or to a-urther treating operation. The rerun still 20 may beutilized to redistill crude pressure distillate from a battery ofpressure cracking stills, the additional crude pressure distillate fromsuch other cracking operations being introduced .thereto throughconncction 30. The rerun pressure distillate bottoms may be passeddirectly to the storage tank 26 through lines 27 and 28 by the pump` 29.Where it is desirable to subject the crude pressure distillate to adesulphurizing treatment prior to the redistilling operation the crudepressure distillate may be discharged d ircctly to thc desulphurizingoperation-from receiver 18 through connection 31 and this desulphurizedstock, together with any other` oil requiring distillation, may beintroduced to the rerun still through the connection 32, the bottomsfrom such redistillation being discharged through connection 33. Tar mayaufk several. preferably operated at substantially atmospheric pressure.The sensible heat contained in the pressure tar may thus be utilized toassist in the evaporation of the volatile constituents upon lowering ofpressure. rhe pressure still, for example, may be operated under apressure of to 150 pounds per square inch. Connection 36 is provided fordraining the pressure still at the end of the run, and the pressure tarso Withdrawn may be pumped to a coke still by the pump 37 throughconnection 38. The coke stills and rerun stills may be of the ordinaryshell type provided with reflux towers and mounted in suitable turnacestructures. The coke still 35 is provided with a valved'connection 39for withdrawing heavy residue when it is not desired to continue thedistillation to coke. The vapors generated in the still 35 pass throughthe reflux tower 40 to the condenser 41. rEhe distillate may beWithdrawn through valved connection 42 or passed directly to the tank 26through pipe 43 by the pump 44. ln addition to the crude pressuredistillate bottoms and coke still .distillate supplied to the tank 26through connections 28 and 43 respectively, fresh oil may be su pliedthereto through valved connection 6%'.

` The tank 26 is connected with the mechanical i treater 45 by valvedconnection 46. The

mechanical treater consists of a series of cells located .one aboveanother and with rotary disks or bames carried by a vertical shaft.These rotary disks are arranged at approximately the center of each cellbetween sidev tively. sowing ont@ ai@ highest disk at ai@ top of thetreater, are caused to interminfgle as they How down over successivedisks and are thrown by centrifugal force against the walls of theapparatus, their intermixture being promoted by the resulting impact.The mingled oil and acid are collected by the. side baliies anddelivered to the next lower disk. Leading from the bottom of the treateris an outlet for the oil and acid tar which are pumped by the pump 48through the` pipe 49 to the settler 50, or to the irst of a series ofsettlers. In such settlers the acid-tar separates from the oil and theoil overdows through the pipe 51 either to another settling tank or areceiving tank 52 for the acidtreated oil, while the acid sludgecollecting in the bottom of the settling tank is drawn olf throughconnection 53 and pumped for example, to an acid recovery plant. Fromthe tank 52 the acid-treated oil passes through the pipe 54 to themixing apparatus 55 to Which clay or fullers earth from the storage bin56 is supplied in regulated amounts. The acid-treated oil, before beingsubjected to the earth treatment, may advantageously be heated, forexample approximately to 175o F., and a steam coil 63 is provided intank l52 for'ths purpose. The treated oil is thoroughly agitated withthe clay' or fullers earth and when the treatment is completed, the oiland earth are pumped by pump 60 through the line 57 to a pressure filter61 from which the finished oil is discharged at 62. In the treatment ofoils containing relatively less refractory sulphur compounds,

the acid treatment may be omitted and the.4

earth treatment relied upon entirely.' `By.-

pass connection 64 and pump 65 are provided to supply oil from the tank26 directly to the receiving tank 52. The earth and oil mixture from thetreater 55 may be permitted to settle before being subjected to the lterpressing operation and only the relatively.

clear oil charged to the filter press. The earth and oil mixture fromthe treater 55 may accordingly be directed to either of the-settlers 58or 59. and after standing the required length of time the settled oi-lmay be `withdrawn through the swing lines 66. The filtered oil isdelivered to the charging stock storage tank 11 through line 68 by thepump 69. The tank y11 is provided with valved connection 70 throughwhich additional substantially sulphur-free oil may be supplied, suchthe equilibrium content of sulphur and su'll phur compounds can be keptat a value materially promoting the economy and efficiency yof thepressure still operation.

j I claim:

1. The improvement in the cracking of heavy hydrocarbon oils for theproduction of lighter hydrocarbon oils therefrom, comprising distillingthe heavy hydrocarbon oils under pressure and at a cracking temperature,supplying fresh oil to this cracking operation and 4withdrawing tartherefrom, subjecting the tar withdrawn from the cracking operation todistillation at a lowerp'ressure, subjecting the distillate from thevtar distillation to a desulphurizingtreatment, and returning thedesulphu-rized tar distillate to the' first mentioned crackingoperation.` Y

2. The improvement in the cracking of heavy hydrocarbon oils for theproduction oflighter hydrocarbon oils therefrom, comprising distillingthe heavy hydrocarbon oils under pressure and at a cracking temperature,supplying additional heavy oil to this 'i cracking operation andwithdrawing tar` therefrom, subjecting the tar withdrawn from thecracking operation to distillation, at'V a lower pressure, commingling`the distillate from the t'ar distillation with fresh oils, subjectingthetardistillate and admixed fresh oil to a desulphurizing treatment andsupplying the desulphurized oil mixture to the first mentioned crackingoperation.

3. The improvement in the cracking of heavy hydrocarbon oils for theproduction of lighter hydrocarbon oils therefrom, comprising distillingthe heavy' hydrocarbon oils under pressure and at a crackingtemperature, supplying additional heavy oil to the cracking operationand withdrawing tar therefrom, subjecting the tar i withdrawn from thecracking operation to distillation at a lower pressure, subjecting thedistillate from the tar distillationto a desulphurizing treatment,returning the desulphurized tai distillateto the first mentionedcracking operation, and vsubjecting the additional heavy oil to besupplied to the irstmentioned cracking operation to a desulphurizingtreatment.

4. The improvement in the cracking of' heavy hydrocarbon oils for theproduction of lighter hydrocarbon oils therefrom, comioo prisingdistilling the heavy oils under pressure and at a cracking temperature,fractionating -the crude pressure distillate obtained from this crackingoperation, commingling a heavier fraction from the fractionation of thecrude pressure distillate with fresh oil and subjecting the oil mixtureto a desulphurizing treatment, introducing the desulphurized oil'mixtureto the 'first mentioned cracking operation, and withdrawing tartherefrom.

5. The improvement in the cracking-ofy heavy hydrocarbon oils for theproduction` of lighter hydrocarbon oils therefrom, comprising distillingthe heavy hydrocarbon oils undery pressure and'. at a ycrackingtemperature, supplying additionalheavy oil to this cracking operationand withdrawing'. tar therefrom, fractionating the pressure distillateand subjecting the tar withdrawn from the lcracking operation todistillation, rey

cycling a heavier fractionl from the frac tionation 'of the crudepressure distillate and the distillate from the tar distillationfto`the4 first mentioned cracking operation, and subjecting the additionaloil to'be supplied to` the cracking operation and the fractions to berecycled to a desulphurizing treatment be-` fore supplying them 'to thefirst mentioned cracking operation. 6. Tha-improvement in the crackingof heavy hydrocarbon oils for the roduction of lighter hydrocarbon oilsthere rom, comprising distilling the heavy hydrocarbon oils y undervpressure and at a cracking temperature supplying additional heavy oilto this t cracking operation and withdrawing tar therefrom, subjectingthe crude pressure distillate obtained from the cracking operation to adesulphurizing treatment and fractionating the desulphurized pressuredistillate, subjecting the tar withdrawn fromthe' cracking operation todistillation, subjecting the distillate from-the tar distillationtogether with additional heavy oil to be supplled to the crackingoperation to a desulphurizing treatment, and introducing thedesulphurized additionalheavy oil and tar distillate together with aheavier fraction of the desu phurized pressure distillate to the firstmentioned cracking operation.

In testimony whereof I have subscribed my name'. Y

. EUGENE C; HERTI-IEL.

